The invention relates to the guidance, positioning and placement confirmation of intravascular devices, such as catheters, stylets, guidewires and other elongate bodies that are typically inserted percutaneously into the venous or arterial vasculature, including flexible elongate bodies. Currently these goals are achieved using x-ray imaging and in some cases ultrasound imaging. This invention provides a method to substantially increase the accuracy and reduce the need for imaging related to placing an intravascular catheter or other device. Reduced imaging needs also reduce the amount of radiation that patients are subjected to, reduce the time required for the procedure, and decrease the cost of the procedure by reducing the time needed in the radiology department.
The vasculature of mammals has long been accessed to provide therapy, administer pharmacological agents and meet other clinical needs. Numerous procedures exist in both venous and arterial systems and are selected based on patient need. One challenge common to all vascular-based therapies is health care provider access to the specific location or section of the vascular tree.
One common venous access procedure is central venous access. Central venous access is the placement of a venous catheter in a vein that leads directly to the heart. Central venous catheters are ubiquitous in modern hospital and ambulatory medicine, with up to 8 million insertions per year in the U.S. and a similar number outside the U.S.
Venous access devices are most often used for the following purposes:    Administration of medications, such as antibiotics, chemotherapy drugs, and other IV drugs    Administration of fluids and nutritional compounds (hyperalimentation)    Transfusion of blood products    Hemodialysis    Multiple blood draws for diagnostic testing.
Central venous access devices are small, flexible tubes placed in large veins for people who require frequent access to their bloodstream. The devices typically remain in place for long periods: week, months, or even longer.
Central venous access devices are usually inserted in 1 of 3 ways:                a) Directly via a catheter. Catheters are inserted by tunneling under the skin into either the subclavian vein (located beneath the collarbone) or into the internal jugular vein (located in the neck). The part of the catheter where medications are administered or blood drawn remains outside of the skin.        b) Through a port. Unlike catheters, which exit from the skin, ports are placed completely below the skin. With a port, a raised disk about the size of a quarter or half dollar is felt underneath the skin. Blood is drawn or medication delivered by placing a tiny needle through the overlying skin into the port or reservoir.        c) Indirectly via a periphal vein. Peripherally inserted central catheter (PICC) lines, unlike central catheters and ports, are not inserted directly into the central vein. A PICC line is inserted into a large vein in the arm and advanced forward into the larger subclavian vein.        
Central catheters and ports are usually inserted by a surgeon or surgical assistant in a surgical suite. An alternative is placement under the guidance of a special x-ray machine so that the person inserting the line can make sure that the line is placed properly. A PICC line can be put in at bedside, usually by a specially trained nurse. In this later case, confirmation by X-ray is currently required for assessing the success of the PICC placement.
Traditional surgically placed central catheters are increasingly being replaced by peripherally inserted central venous access devices. PICC lines usually cause fewer severe complications than central venous access devices. Peripherally-Inserted-Central-Catheter (PICC) is used in a variety of clinical procedures. The PICC line placement procedure is performed by interventional radiologists to deliver long-term drug delivery, chemotherapy procedures, delivery of intravenous medications or intravenous nutrition (hyperalimentation) and taking blood samples via a Hickman catheter. Insertion of PICC lines is a routine procedure in that it is carried out fairly often for a variety of treatments, and more than once in the same patient when the catheter is to be left in place for any length of time. Even though it is routine, it is a very time and labor-intensive procedure for the hospital staff, which also makes it expensive. During the procedure the physician or nurse places the catheter into a superficial arm vein such as the cephalic, basilic, antecubital, median cubital, or other superficial vein with the goal of having the distal end of the catheter reach the superior vena cava. After entering the superficial vein around the area where the arm bends (elbow), the catheter is advanced up the subclavian vein, then the brachiocephalic vein and finally it enters the superior vena cava. One caveat is to make sure that the PICC line does not enter the jugular vein via the subclavian vein.
Pulmonary artery catheterization is another example of a procedure utilizing venous access procedures. Pulmonary Atery Catheters (PAC), also knows as Swan-Ganz or right heart catheters, provide information regarding the central venous, right heart, and pulmonary arterial blood pressures, thermodilution measurements that are useful for calculating cardiac output and related physiological parameters, access for drug delivery, and blood sampling at various intervals along the length of the catheter. PACs can lead to several complications in a patient. These complications include arrhythmias, rupture of the pulmonary artery, thrombosis, infection, pneumothorax, bleeding, etc. Complications can arise due to improper insertion, use, and/or maintenance of the catheter in the patient.
Hemodialysis therapy via a hemodialysis catheter is another example of a procedure requiring central venous access. A dialysis catheter is a specialized type of central venous catheter used for dialysis. Dialysis catheter placement involves the insertion of a catheter into a large vessel, utilizing X-ray guidance. The challenges of inserting a hemodialysis catheter in terms of guidance and positioning are similar to those of a central venous catheter, only they are typically larger and require a peel-away sheath for insertion.
Another therapy achieved via providing access to the venous system is the percutaneous treatment of varicose veins. Published population studies indicate that approximately 25 million people in the U.S. and 40 million people in Western Europe suffer from symptomatic venous reflux disease. Percutaneous treatment of varicose veins involves the placement of an energy delivery catheter (laser or RF) after navigation the vasculature to locate the treatment site. One common treatment site is the sapheno-femoral junction and less common sites are the sapheno-popliteal junction and sites of perforator veins, which connect the superficial venous system to the deep venous system of the leg at a variety of different locations, mostly below the knee. As such, in the case of percutaneous treatment of varicose veins using specific venous junctions, the position the laser or the RF catheter at an optimal location with respect to the venous junction is critical for the success of the intervention.
In addition to guiding the catheter through the vasculature, the location of the catheter tip is very important to the success of the procedure. Catheters will generally function equally well for pressure measurement and fluid infusion if the tip is situated in any major vein, above or below the heart. For dialysis or the infusion of irritant/hypertonic fluids, a high rate of blood flow past the catheter tip is desirable and this requires the placement of the luminal opening in as large a vessel as possible. However, the package inserts of many central venous catheters give very strong warnings about the absolute requirement for catheter tips to lie outside the heart to avoid perforation and subsequent pericardial tamponade. Likewise positioning the catheter tip away from small peripheral veins is important to avoid damaging the vein wall or occluding the vein due the caustic effects of the infusing solution. It is also of major interest that the catheter tip stays in place after placement for the whole duration of the treatment. If the catheter tip moves, not only its effectiveness diminished but, in some situations, it can perforate the heart. In the United States, the Food and Drug Administration has issued advice emphasizing this point. Typically, the interventional radiologist uses a fluoroscopic agent to delineate the veins in the body and subsequently verifies the correct positioning of the catheter tip using a post-operative X-ray. Currently, post-operative X-ray is performed routinely while some studies have shown that only 1.5% of the cases are subject to complications that would indeed require X-ray imaging.
Current methods for guiding PICC lines include external electromagnetic sensors and intravascular, e.g, ECG. N the case of electromagnetic sensors, the endovascular device is guided by assessing the distance between an electromagnetic element at the tip of the device, e.g., a coil and an external (out of body) receiver. This method is inaccurate because it does not actually indicate location in the vascular but distance to an outside reference. In the case of ECG-guided catheters, the classic increase in P-wave size, known as ‘P-atriale”, is a widely accepted criterion for determining location of central venous catheter tips in the proximity of the sino-atrial node. Current methods include using a catheter filled with saline and an ECG adaptor at the proximal end connected to an ECG system. This method is inaccurate because it does not indicate location in the blood vessel but the proximity of the sino-atrial node. Because of known inaccuracies, all the current methods in use do explicitly require the use of a confirmatory chest X-ray to verify and confirm location of the tip of the endovascular device at the desired target in the vasculature. Most prior art relating to the use of intravascular ultrasound or electrical mapping of heart activity for diagnostic and therapeutic purposes addresses problems independently: some addresses ultrasound guidance on the arterial side such as that described by Franzin in Doppler-guided retrograde catheterization using transducer equipped guide wire (U.S. Pat. No. 5,220,924) or that described by Katims in Method and apparatus for locating a catheter adjacent to a pacemaker node of the heart (U.S. Pat. No. 5,078,678). Such approaches have intrinsic limitations which does not make them suited to solve the problem addressed by the current invention. The limitations of the Frazin approach have been extensively explained in VasoNova patent applications US 20070016068, 20070016069, 20070016070, and 20070016072. Limitations of an approach based exclusively on measuring right-atrial electrocardiograms have been described in the literature, for example in [1]: W. Schummer et al., Central venous catheters—the inability of ‘intra-atrial ECCG’ to prove adequate positioning, British Journal of Anaesthesia, 93 (2): 193-8, 2004.
What is needed are methods and apparatuses to optimize guidance and placement of catheters in order to reduce the risk associated with wrong placement and the cost associated with the X-ray imaging. Further there remains a need for a catheter guidance and placement system that may be used to safely guide and place catheters in healthcare provider or clinical environments other than in the radiology department or surgical suite wherein a radiological or other external imaging modality is used to confirm catheter placement. As such, there remains a need in the medical arts for instruments, systems and associated methods for locating, guiding and placing catheters and other instruments into the vasculature generally. In addition remains a need in the medical arts for instruments, systems and associated methods for locating, guiding and placing catheters and other instruments into the vasculature to meet the challenges presented by the unique characteristics and attributes specific to the vascular system of interest. The current invention overcomes the above described limitations by making use of physiological parameters like blood flow and ECG measured in the vasculature and is based on the fact that physiological parameters and their relationship is unique to the locations in the vasculature where the endovascular devices needs to be placed. The current invention describes an apparatus for identifying the unique physiological signature of a certain location in the vasculature and a method to guide the endovascular device to that location based on the physiological signatures.